4G networks are the fourth generation of mobile telecommunication technology standards, and include the WiMAX and LTE-Advanced network standards. The 4G networks include a new architecture to support a small-scale evolved Node B (eNodeB), which may be installed in private homes (known as a femto access point, or femtocell), or outdoor areas (known as metrocells or picocells, depending on the coverage area). These cells are collectively known as small cells.
Small cells are expected to be widely adopted. However, as small cells are designed to be deployed by end-users with minimal intervention from Mobile Network Operators (MNOs), several issues arise. For example, if two small cells have overlapping coverage areas (as shown in FIG. 1) but transmit using the same frequency and time slots, then signals from these two small cells will interfere with each other and data throughput is significantly reduced. This form of interference is known as co-tier, as the interference is between two elements on the same tier of the network. There may also be interference between signals from the macrocell and small cell when they use the same frequency and time slots, known as cross-tier interference. To address these issues and minimize interference in the network, MNOs employ various resource management techniques.
A first example of a conventional resource management technique involves a small cell determining the resources used by other small cells and allocating its resources and power usage accordingly. In a second example, a centralized resource management system determines the topology and resource demands of the network and allocates the resources to each small cell. In both these examples there is an extra processing demand imposed on the small cells, as they must determine and report their resource allocations and process any signals received from other small cells or the management system. Furthermore, there is an increase in control traffic on the network to carry all these extra signals, which may be significant for extensive small cell deployment.
A third example of a conventional resource management technique involves a small cell independently determining its resource allocation. This technique is more desirable than the two examples above, as the processing burden on the small cell is relatively small and it does not increase the control traffic on the network. There are several implementations of this technique. Firstly, the small cells may each allocate their own resources randomly (for example, by using a random or pseudorandom number generator). Although this simplifies the computation, it results in a greater level of interference compared to the first and second examples detailed above. This problem is exacerbated by such number generators producing ‘clusters’ of numbers (i.e. wherein parts of a sequence have a greater density of points compared to others).
An improvement of the independent resource management technique involves small cells using various parameters to calculate their resource allocations. These parameters may include the data rate required by users or the measured interference for each resource block. The small cell may determine these parameters from measurement reports from a User Equipment (UE). This technique produces an improved resource allocation (i.e. less interference) than the random technique above, but incurs a penalty of increased traffic between the small cell and UE.
Given the limitations of the independent techniques, small cell vendors have generally opted for the first and second examples above. However, there are further complications as small cells from separate operators (using incompatible techniques) will be deployed in the same coverage area.
US Patent Application Publication Number 2008/0233966 A1 discloses a method of pseudorandom resource allocation in OFDM communication systems. This disclosure therefore suffers from the issues of random and pseudorandom allocation discussed above.
It is therefore desirable to alleviate some or all of the above problems.